Milk fats contain a relatively high proportion of glycerides of saturated fatty acids. Such glycerides have relatively high softening temperatures; as the temperature of the butter is decreased by refrigeration, for example, the hardness of the butter increases greatly whereby it becomes no longer spreadable. It would be highly desirable to decrease the concentration of these fatty acids in butter so that the butter is spreadable at lower temperatures, particularly where this can be achieved whilst retaining the plastic characteristics of butter at normal ambient temperatures. It would be further desirable to achieve this decrease in the concentration of saturated fatty acids as these are considered by many authorities to be linked to blood cholesterol formation.
The rheological properties of margerin have long been known to be influenced by varying the fatty acid make-up of the glycerides and also the water content of the emulsion. Whilst it would be possible to modify the chemical make-up of butter fat, e.g. by transesterification, such product would no longer be a true dairy product.
It has heretofore been proposed to reduce the fat content of butter by increasing the water content thereof. In such proposals butter is first prepared from cream by churning in the traditional manner, and water is reincorporated as a second step. It would be economically desirable to produce a low fat product from cream in a one step process.
Furthermore, the churning process for the manufacture of normal butter is essentially a batch process. It would be desirable to produce butter from cream as a continuous process.
Natural butter comprises a water in oil emulsion of about 80% milk fats, 17% water, 1% to 2% milk solids not fat (milk solids) and up to about 2% salt; minor quantities of other adjuvants may also be present. It is generally produced by churning dairy cream having up to about 40% milk fat, 6% milk solids, with the balance water. In the churning process a phase inversion occurs when the separation of buttermilk from the butter produced, and a concomitent increase in fat content and decrease in milk solids. Since the milk solids are predominately protein it is apparent that there is a loss of nutritional value in the formation of natural butter from cream. It would be desirable to produce a low fat butter having the nutritional balance in terms of protein to fat ratio about equal to that of dairy cream.
It is known to produce low fat dairy spreads directly from cream. However, in such processes the product is an oil in water emulsion. The continuous aqueous phase with its relatively high protein content forms an excellent medium for the propagation of micro-organisms, and such products have little commercial acceptance for this reason. Even where the aqueous phase is discontinuous, it may still be conducive to bacterial propagation, particularly where the protein of the product is relatively high as herein. It would be desirable to provide a nutritional, low fat butter of good keeping quality.